A motorist travels from Town A to Town B at a constant speed of 60\text{ km/h} for 2\text{… — JAMB UTME

A motorist travels from Town A to Town B at a constant speed of $60\text{ km/h}$ for $2\text{ hours}$ , and then continues from Town B to Town C at a constant speed of $90\text{ km/h}$ for $3\text{ hours}$ . What is the average speed of the motorist for the entire journey in $\text{km/h}$ ?

Answer: 78 km/h

Answer

The average speed for the entire journey is

78\text{ km/h}

The correct average speed is

78\text{ km/h}

, obtained by dividing the total distance of

390\text{ km}

(

120\text{ km} + 270\text{ km}

) by the total duration of

5\text{ hours}

(

2\text{ h} + 3\text{ h}

Step-by-Step Solution

Find the distance traveled during each segment of the journey

First segment distance =

120\text{ km}

, second segment distance =

270\text{ km}

Distance equals speed multiplied by time (

D = v \times t

Determine the total distance traveled and total time taken

Total distance =

390\text{ km}

, Total time =

5\text{ hours}

Average rate requires the sum of all distances and the sum of all durations.

Calculate the average speed

Average speed =

78\text{ km/h}

Average speed is defined as total distance divided by total time.

Key Concept

Average Rate and Speed

Question

Answer

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